gertfire1

Sprinter engine power reduced possibly defective relay

My 2013 Mercedes Sprinter, gasoline engine, with 62037 km is having a strange issue. The engine power is significantly reduced and the error memory shows a fault related to the engine control unit. I've checked basic things like fuses, but nothing seems obviously wrong. Could a defective main relay cause this kind of issue and impact the automotive electronics? I'm wondering if a simple system reset would solve this or if it points to deeper ECU problems.

4 comment(s)

Sounds like what happened to my Sprinter once. Reduced power, ECU errors popping up. I'd put money on the main relay being the culprit. It's like a gatekeeper for the ECU; if it's failing, the ECU doesn't get consistent power, throws errors, and limits performance. Check that relay with a multimeter; it should be a straightforward check.

Thanks for the quick response. Where exactly is the main relay located on your Sprinter? Also, when you say straightforward check, did you mean just testing for voltage, or something more involved than that?

Location can vary slightly, but usually it's in the main fuse box under the driver's seat. Check your vehicle's manual, it should be labeled. As for the check, a simple voltage test will tell you if it's providing power, but the best way to test it is to replace it with a new one. If that resolves the problem, you know for sure. Still, I would recommend you to get a professional opinion on the ECU problems: the system reset might not be enough.

It was indeed the main relay causing all the trouble. After replacing it, the engine power is back to normal, and the error code is gone. The final repair cost was around 120€. I appreciate your advice.

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